This invention relates to composite particles for composite dispersion plating and to a plating method using the same, and more particularly to composite particles for composite dispersion plating used for a self-lubricating composite dispersion plating film and to a plating method and a plating film or coating that make use of these particles.
Composite dispersion plating is a method whereby dispersion particles composed of ceramic particles such as SiC, Si3N4, BN are codeposited in a plating film composed of a metal matrix of nickel or the like. It is essential that the dispersion particles be suspended in the plating bath. Composite dispersion plating films (such as an Nixe2x80x94Pxe2x80x94BN plating film) are known to be plating films with low friction, and have been applied to sliding member surfaces in internal combustion engines and the like.
Thus, to suspend dispersion particles in a plating bath by the codeposition of dispersion particles with a low specific gravity in a plating bath, the most common approach is to add a surfactant to the plating bath, but this causes various problems, such as the generation of bubbles in the plating bath and changes in the internal stress of the plating film.
An example of a method for the codeposition of dispersion particles with a low specific gravity in a plating bath without the addition of a surfactant is a method in which core particles (mother particles) composed of an organic substance are encapsulated with shell particles composed of a ceramic to form composite particles, and these composite particles are codeposited as dispersion particles in a plating bath (Japanese Patent Application Laid-Open Publication No. 8-41688).
A method in which carbon (graphite), which has excellent friction reducing properties, is codeposited as dispersion particles or composite particles has been tried in an effort to diminish the adverse effect on mated sliding members, that is, in an effort to obtain a plating film with lower friction.
However, no matter which conventional method is used (a method in which a surfactant is added to the plating bath, or a method in which composite particles are codeposited in the plating bath), it is extremely difficult for particles with a very low specific gravity, such as carbon, to be codeposited as dispersion particles or composite particles in a plating bath.
In view of this, an object of the present invention is to solve the above problems and provide composite particles for composite dispersion plating constituted by particles having excellent friction reducing properties and a low or very low specific gravity, and a plating method in which these composite particles are used.
The composite particles for composite dispersion plating according to the present invention are produced by the encapsulation of the surface of a core particle having excellent friction reducing properties and a low specific gravity with shell particles composed of the same components as the base metal of the composite dispersion plating bath.
It is preferable here for the core particle to be composed of carbon. This will allow composite particles for composite dispersion plating with excellent friction reducing properties to be obtained, which in turn allows a composite dispersion plating film with lower friction to be obtained. Alternatively, the core particle may be Fe3O4.
It is also favorable for the shell particles to be selected from among nickel (Ni), copper (Cu), tin (Sn), aluminum (Al), chromium (Cr), iron (Fe) and zinc (Zn). This will cause the shell particles to dissolve in the base metal of the plating film during the formation of the composite dispersion plating film, and as a result the core particles themselves will be dispersed in the plating layer.
The composite particles for composite dispersion plating is constituted by particles with excellent friction reducing properties and a low or very low specific gravity.
The plating method that makes use of composite particles for composite dispersion plating pertaining to the present invention is such that the material to be plated is immersed in a composite dispersion plating bath produced by the codeposition of composite particles in which the surface of a core particle used for reducing friction is encapsulated by shell particles composed of the same components as the base metal of the composite dispersion plating bath, after which a plating film in which the composite particles have been codeposited in the plating layer is formed on the surface of the material to be plated.
It is preferable here for the composite particles to be formed by mixing the core particles used for reducing friction with the shell particles composed of the same components as the base metal of the composite dispersion plating bath in a predetermined weight ratio, and then performing mechanical encapsulation.
It is also preferable for an electrolytic material to be immersed along with the material to be plated in the composite dispersion plating bath, and then for electroplating to be carried out using the material to be plated as the cathode and the electrolytic material as the anode to form the plating film.
It is also preferred that the plating solution of the composite dispersion plating bath is circulated and air is blown into the plating bath to agitate the plating solution during the electroplating.
The material to be plated is preferably moved up and down during said electroplating.
With the plating method utilizing the composite particles for composite dispersion plating according to the present invention, particles with excellent friction reducing properties and a low or very low specific gravity can be been codeposited in the plating layer without the addition of a surfactant.
The plating film which makes use of composite particles for composite dispersion plating pertaining to the present invention is produced by codepositing in the plating layer composite particles in which the surface of a core particle used for reducing friction is encapsulated by shell particles composed of the same components as the base metal of the composite dispersion plating bath.
The plating film which makes use of composite particles for composite dispersion plating pertaining to the present invention can be applied to sliding members in internal combustion engine (xe2x80x9cenginexe2x80x9d) parts. For example, if the composite dispersion plating film which makes use of composite particles for composite dispersion plating according to the present invention is formed on the inner surface of a cylinder, the inner surface of a cylinder liner, the sliding surface of a piston, the sliding surface of a cylinder block, the sliding surface of a connecting rod big end, or the surface of a crankshaft in slidable contact with the connecting rod, a plating film of lower friction than conventional low-friction plating films will be formed on the surface (sliding surface) of these various members, thereby reducing the adverse effect on mated sliding members.